The present invention relates to an explosive priming device, more particularly of the type comprising a pill of explosive material.
It is known that for every type of explosive device, both in form of a projectile (this word having to be understood in its most general meaning), or in form of an explosive chain, there is necessary a primer normally comprising a highly explosive material which, owing to a mechanical, chemical or thermal action, generates high temperature and/or pressure gases, capable of activating the explosion of the main explosive charge or of the subsequent charge in the case of an explosive chain.
The problems and drawbacks of the already known primers and their importance do not need much comments: it is enough to remember that the successful outcome or the failure, from the point of view of the operation, of the projectile depends on the right operation of the priming device. According to the conventional embodiments, the priming devices are inserted in the bottom of the projectile, so as to be struck by the percussion pin and start the explosion of the main charge. Such a construction gave place to a strong limitation as regards the use of the subject projectiles and particularly as regards the firing rate, owing to the need of taking into account, in the operating sequence, also the step of the cartridge-case ejection.
Furthermore, but not of less importance, there exists the problem of the storage and of the handling of the explosive devices, which require, owing to the presence of the primers (highly sensitive), particular care and cautions, under penalty of accidental explosions with very serious consequences.
In the field of particular explosive operated devices, namely of the tools capable of driving nails and like pointed elements due to the action of an explosive charge, in recent years there appeared the models in which the explosive charge for the driving of the point or nail consists of a pill of an explosive material, possibly coated with a protection paint, the percussion of this pill giving place to the desired explosion, without the need of cartridge cases or of priming caps and without the necessity of foreseeing, in the firing sequence, a step for the case ejection. With reference to this type of explosive charge there has also been described a firing device for explosive pills of the aforesaid type, particularly applied to the aforesaid tools for driving pointed elements and nails, this device comprising an explosion chamber of frusto-conical shape, having blind bottom and of suitable size, the explosive pill being positioned against the open end of the chamber: the percussion of the pill causes the same or a central portion thereof to penetrate into the said explosion chamber with an adiabatic compression of the air present in the same chamber whereby the air achieves, practically instantaneously, temperature and pressure conditions such as to ensure the explosion of the pill.